The present invention relates to a highly integrated solar array wing capable of survival in a low-earth-orbit (LEO) environment and capable of multiple deploy/restow cycles per mission and multiple mission capability without refurbishment.
Current solar array designs that possess restow capability are limited to flexible solar cell substrates that are subject to atomic oxygen erosion and contain complex mechanization to re-fold the array into the stowed volume. All of the arrays of this type are not intended or designed for complete re-stow and re-use.
Compact retractable arrays consist of photovoltaic cells mounted to flexible substrates. LEO missions must address damage to the substrate resulting from exposure to atomic oxygen over time. Additionally, the flexible substrates must fold in a predictable fashion to assure that cell damage does not occur during the stow cycle. Controlling the fold lines requires very complex mechanical elements that diminish operational reliability. No known prior art system has been designed for complete re-use and multi-mission capability. Some military satellite systems would benefit from the ability to completely re-stow because this would offer mission flexibility to move the satellite thus making its orbit unpredictable.
U.S. Pat. No. 3,326,497 for Solar Cell Array discloses a solar cell array panel used on space vehicles. The array is actually deployed on a number of hinged panels so that the array may be folded compactly and stowed on the side of the space vehicle. When fully extended, the hinged panels may be rotated to orient the surface of the solar cells perpendicular to the impinging light rays.
U.S. Pat. No. 4,384,163 for Ultra Lightweight Folding Panel Structure discloses an un-foldable planar solar cell array which may be deployed from the cargo bay of a space shuttle using an extendable boom.
An article published by IEEE in 1988 and entitled xe2x80x9cRetractable Advanced Rigid Arrayxe2x80x9d by J. DeKam, describes a retractable solar array for use on satellites which may be stowed in the cargo bay of a space shuttle for deployment and retrieval in low earth orbit.
As can be seen, there is a need for a foldable, non-flexible solar cell array that may be stowed in the payload bay of a reusable space vehicle without using a significant amount of storage volume.
The present invention provides a deployable/foldable solar cell array which provides a solution for a robust solid substrate design. The complete Solar Array Assembly (SAA) is a six degree of freedom (6DOF) mechanism that articulates the cell substrates out of a stowed volume (payload bay) to a determined orientation for solar array articulation relative to the sun, optimum power generation, and mission operations. This array is designed for multiple usage on a reusable space plane such as Boeing""s X-37 and SMV projects. It incorporates motor deployment of four panels and a solar array boom which may be stowed in the vehicle""s payload bay. This system is designed for multiple Deploy and Re-Stow over the life of a 40 mission SMV (Space Maneuver Vehicle). The packaging of the array is unique in that it takes only 6.6 cubic feet in the payload bay of the X-37/SMV. The stowing latches that are normally required for solar array systems are not necessary as the inventive array is passively stowed on fixed snubbers and the system employs a unique integral door design for preloading the stowed assembly when the payload bay doors are selectively closed to enclose the solar array assembly.
The invention comprises the following major elements in one embodiment:
The four panels are shaped to be substantially congruent to the payload bay doors when the panels are folded in their stowed configurations. Two inboard panels are connected on each of their respective facing edges to a symmetrically located, elongated structural boom extending along substantially the entire length of the panels.
The solar array arm deployment is carried out in a coordinated set of moves that are preprogrammed into the flight software. Go/No Go position switches and sensors are employed for proper sequencing. The array, once deployed off to the side of the spacecraft, has a two-axis drive (SADPT) that can be mission scenario driven in two distinct orthogonal axes of rotation (Alpha and Beta).
The inventive design offers a reliable solution that meets the program requirements. To date, no aerospace company has apparently produced a multiple use restowable array design for a reusable unmanned spacecraft/space plane. Its applications could also prove beneficial to satellite missions for quick orbit modification for planned mission unpredictability.